Health officials in Uganda say they have identified a strain of the deadly Ebola virus as the likely killer of at least 16 people in the west of the country since late August. But as VOA Correspondent Alisha Ryu reports from our East Africa Bureau in Nairobi, officials are baffled and worried by what they believe is a new strain of the hemorrhagic fever.

The director general of Uganda's health services, Dr. Sam Zaramba, tells VOA that scientists in South Africa and the United States conducted numerous laboratory tests to determine the cause of the deaths across 14 villages in the western district of Bundibugyo.

Electron micrograph of Ebola virus

Dr. Zaramba says he was dismayed to learn this week that some of the blood samples sent to the laboratories had tested positive for the virus that causes Ebola.

"The first three samples of blood that we sent proved negative of hemorrhagic [fever] disease," he said. "But early this week, we sent another 20 samples and out of the 20 samples, eight of them were positive for Ebola."

The disease was first identified more than 30 years ago in Sudan and in Congo Kinshasa. It spreads rapidly and kills between 50 to 90 percent of infected people. There is also no known cure.

Dr. Zaramba says the current outbreak in western Uganda is particularly worrisome because it is a strain of the Ebola virus that scientists have never seen before.

"It is definitely different. Even the symptoms are different," said Dr. Zaramba. "Whereas the other ones are characterized by bleeding from orifices, this particular one, instead of the bleeding, we have a rash, measles-type of rash."

Since 1976, four sub-types of the hemorrhagic fever have been identified, all but one being lethal to humans. Common symptoms include extremely high fever and bleeding from openings in the body.

Dr. Zaramba says he believes the new virus spreads much like the other strains - through close contact with the body fluids of an infected person or someone who has died of the disease.

He says a new team of experts has traveled to Bundibugyo to help isolate existing cases.

Bundibugyo District is 350 kilometers west of the Ugandan capital Kampala and is not linked to another Ebola outbreak in neighboring Congo Kinshasa. The World Health Organization says it believes Ebola has killed 160 people and has infected 352 others for the past four months in the southern Congolese province of Kasai Occidental.

The last Ebola outbreak in Uganda occurred seven years ago in the northern district of Gulu. Of 426 people diagnosed with the disease, more than 170 died.